Firearm assembly

ABSTRACT

The present invention includes a receiver for a firearm having a front recess to receive a barrel. The receiver has a load/eject recess port open to the front recess and to a side or bottom of the receiver to allow the insertion and removal of a cartridge from the receiver. A slit along the front recess and the load/eject recess port together form a single opening along the receiver whereby the receiver can expand to allow the insertion of a barrel into the front recess. Included is a firearm having the receiver of the invention.

BACKGROUND OF THE INVENTION

Various methods and configurations for safe and reliable firearms havebeen developed in the storied history of small arms development. Withthe advent of smokeless powder in the late 19th century, and thesubsequent development of more powerful chamberings in the early 20^(th)century, bolt-action firearms were developed as a way to handle theincreased pressures of firing these larger, more powerful rounds. Theseimprovements have continued to develop and advance ballistic performanceand have resulted in some very large cartridges, including the 0.50 BMG.

Generally, a bolt-action firearm comprises a bolt which houses a firingpin. The bolt slides within the firearm receiver between a rearwardposition which allows loading and unloading of a cartridge, and aforward position. As the bolt slides forward, the cartridge is pushedforward into a firing chamber. The bolt is then typically closed byrotating it into a battery position, thus locking the bolt behind thecartridge. The firing pin is then activated by pulling the trigger whichcauses the firearm to discharge. To expel the empty casing, the bolt isrotated out of its locked position and slid rearward to extract theempty casing.

As a part of the empty casing extraction, different extractors have beendeveloped. Most throw the casing outward and away from the firearm ineither an upward or sidewise direction. This can cause a variety ofproblems, including striking the user or a bystander, and losing theempty casing which the user often may wish to retain. It is also aproblem in military or law enforcement situations when such movement ofthe flying casing could reveal the location of the shooter. This isespecially undesirable in sniping situations.

Another problem which is often sought to be resolved in a variety ofways includes the prevention of accidental or unintended discharge.Because the firing pin is typically disposed within the bolt, and thebolt (as described above) is typically pushed forward against the rearof the cartridge as the cartridge is advanced into the firing chamber,the potential for unintended discharge of the weapon is present,particularly as the bolt is thrown forward to chamber a round. A varietyof solutions have been developed, with varying degrees of success.

Still another problem encountered with the development of higher chamberpressures is seen in the materials used to build these firearms. Withthe larger pressures generated by the development of larger and morepowerful magnum loads and larger cases, more and more material wasneeded in order to obtain adequate strength. Competing with theseincreased material dimensions, however, is a desire for lighter-weight(and/or less costly) firearms. One way to remedy the weight problem isto use lighter weight materials (e.g., aluminum instead of steel), butstrength problems can result. Thus, some prior art attempts at buildingadequately strong, yet light weight receivers, have included usingaluminum and other light weight materials or alloys where possible inthe firearm. This introduced manufacturing challenges, however, becauseheat treatments and other manufacturing requirements treated thedifferent materials differently.

SUMMARY OF THE INVENTION

The present invention provides a receiver for a firearm comprising afront, at least two sides, and a bottom. The receiver has a front recessto receive a barrel or barrel extension, and is defined by a channel inthe receiver which is open longitudinally along a longitudinal slit inthe receiver. The receiver also has a load/eject recess open to thefront recess and to either a side or bottom of the receiver. Theload/eject recess is sized to allow the insertion and removal of acartridge from the receiver. The slit and the load/eject recess togetherform a single opening to the receiver whereby the receiver can expand toallow the insertion of a barrel or barrel extension into the frontrecess. In a preferred embodiment, the slit and load/eject recess areopen to the bottom of the receiver. The receiver is either biasedagainst the insertion of a barrel or barrel extension, such that it mustbe pried open to allow insertion and its own at rest position (inwardbias) provides a compressive force to hold the barrel in place, or,alternatively, it is biased open and a compressive force, such as abolt, closes the receiver against the barrel or barrel extension.

In a preferred embodiment, the receiver has a front recess to receive abarrel extension, the front recess defined by a channel openlongitudinally at its bottom along a longitudinal slit. Included in thispreferred embodiment is a load/eject recess open to the front recess andto the bottom of the receiver to allow the insertion and removal of acartridge from the bottom of the receiver. Also included in thispreferred embodiment is at least one clamping hole in the receiverdisposed through the longitudinal slit and sized to receive clampingmeans, such as a bolt. The slit and the load/eject recess together forma single opening along the bottom of the receiver. The front recess isexpandable and contractible along the slit whereby the slit iscompressible by the clamping means to apply a compressive force on abarrel extension inserted into the front recess.

Also included as a part of the invention is a barrel extension for afirearm barrel. The barrel extension is suited for insertion into thereceiver of the present invention. In a preferred embodiment, the barrelextension comprises a metallic tube having an outer surface, and aprotrusion extending radially outward from the outer surface of themetallic tube. In a preferred embodiment, the protrusion is a pin.

Still also included in the present invention is a safety mechanism for afirearm to prevent unintentional firing of the firearm. The safetymechanism comprises a bolt having a bolt head disposed at a distal end,a proximal end, and a longitudinal channel disposed in the bolt to housea firing pin. A firing pin is disposed in the longitudinal channel ofthe bolt, and has a distal end at the bolt head and a proximal endextending out of the longitudinal channel to allow activation of thefiring pin by a hammer. A safety bar is disposed at the proximal end ofthe firing pin wherein rotation of the bolt into a firing positionrotates the safety bar into an activation position whereby the firingpin can be activated by a hammer striking the safety bar, and rotationof the bolt into a non-firing position rotates the safety bar out of theactivation position whereby a falling hammer cannot strike the safetybar or firing pin.

Included also is firearm comprising a barrel, a barrel extensionattached to the barrel, the barrel extension having a protrusionextending radially therefrom, and a receiver. The receiver comprises afront, at least two sides, and a bottom, a front recess to receive abarrel or barrel extension, the front recess defined by a channel in thereceiver which is open longitudinally along a longitudinal slit in thereceiver, and a load/eject recess open to the front recess and to atleast one side or bottom of the receiver. The load/eject recess is sizedto allow the insertion and removal of a cartridge from the receiver. Theslit and load/eject recess together form a single opening to thereceiver whereby the receiver can expand to allow the insertion of abarrel or barrel extension into the front recess. The slit accepts theprotrusion to guide the barrel extension into the receiver. A preferredembodiment of the firearm includes the safety mechanism described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of a partial firearm in accordance with the presentinvention with the barrel removed from the receiver;

FIG. 2 is a view of a partial firearm in accordance with the presentinvention as shown in FIG. 1 but with the barrel inserted into thereceiver;

FIG. 3 is a view of a receiver in accordance with the present invention;

FIG. 4 is a view of the underside of the receiver shown in FIG. 3;

FIG. 5 is a view of the front end of the receiver shown in FIG. 3;

FIG. 6 is a view of the receiver of FIG. 3 but with clamping meansshown;

FIG. 7 is a view of a barrel, barrel extension, and bolt in accordancewith the present invention;

FIG. 8 is a view of a bolt incorporating the safety mechanism of thepresent invention where the bolt is in an open position;

FIG. 9 is a view of a bolt incorporating the safety mechanism of thepresent invention where the bolt is in its closed position; and

FIG. 10 is a view of a safety bar in accordance with one embodiment ofthe safety feature of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides several advantages over known firearmconfigurations. These advantages are seen with respect to both safetyand ease of manufacture. One aspect of the present invention is thereceiver. A second aspect relates to a safety mechanism in a novelbolt/firing pin configuration.

FIG. 1 shows a firearm utilizing the receiver aspect of the presentinvention, with the barrel separated from the receiver for illustrationpurposes. Specifically, FIG. 1 shows a firearm 100 having barrel 110,receiver 120, and stock 130. Not shown is the trigger assembly, which isnot necessary to an understanding of the present invention. Muzzle brake140 and utility rail 150 (such as a picatinny rail) for a scope or carryhandle, are also shown. As can be seen in FIG. 1, barrel 110 isintegrally attached to barrel extension 115 in this embodiment.Typically this connection would be a threaded connection, but it couldalso take the form of other connections including welding or adhesives,among others. Barrel extension 115 in turn extends into receiver 120 andis connected to receiver 120 in accordance with the present invention,as shown in FIG. 2. FIG. 2 is the firearm shown in FIG. 1 but withbarrel 110 (along with barrel extension 115) inserted into receiver 120.

FIG. 3 shows receiver 120 in more detail. FIG. 3 shows receiver 120without utility rail 150 attached thereto, without barrel extension 120inserted therein, and without stock 130 attached. As can be seen,receiver 120 has front recess 122 formed therein with slit 125 formedalong the bottom of the front recess. Front recess 122 is configured toreceive either a barrel or a barrel extension. Front recess 122 isdefined by a channel open longitudinally at slit 125. Slit 125 ispreferably disposed along the bottom of receiver 120 as shown in FIG. 3,but could be located on either side of the receiver (not shown) or topside (not shown) so long as it connects to a load/eject port asdescribed more fully below. FIG. 3 also shows utility rail mountingholes 200 and utility holes 210 such as may be used for mounting abipod.

Included as a part of receiver 120 is load/eject recess 160, which canbe better seen in FIG. 4 which is a bottom-angled view of receiver 120.In this preferred embodiment, the slit and load/eject recess are open tothe bottom of the receiver. More specifically, load/eject recess 160 isopen to front recess 122 and to the bottom of receiver 120 to allow theinsertion and removal of a cartridge (or cartridge casing) from thebottom of receiver 120.

FIG. 5 shows an angled front view of receiver 120 and illustrates thecommunication between front recess 122 and load/eject recess 160.Load/eject recess 160 allows direct access to the firing chamber whenthe bolt (shown and discussed below) is open to allow access, throughload/eject recess 160, to the firing chamber at the proximal end of thebarrel or barrel extension. As can be seen in FIGS. 4 and 5, slit 125and load/eject recess 160 together form a single opening along thebottom of receiver 120. In alternative embodiments, the slit and portmay together be positioned on any side of the receiver, including thetop side.

The relationship between the receiver's front recess and the barrel orbarrel extension (the later of which is shown in FIG. 1), can take anumber of forms. The receiver's front recess can: (1) be in a slip-fitrelationship with the barrel or barrel extension in which case it can becompressed by means of compression means (discussed in more detailbelow) after the barrel or barrel extension is inserted; (2) be largerthan the outside dimension of the barrel or barrel extension (even moreso than the case in (1), above), in which case it is also compressed bymeans of compression means (discussed in more detail below) after thebarrel or barrel extension is inserted; or (3) be smaller than the outerdimension of the barrel or barrel extension, in which case it can bemechanically (or otherwise, such as thermally) expanded to allow theinsertion of a barrel or barrel extension into the front recess andallowed to return to its at-rest position and thereby anchor the barrelor barrel extension in place with respect to the receiver.

The combination of slit 125 and load/eject port 160 to form a singleopening achieves several advantages. One advantage relates to theconnection of the barrel or barrel extension to the receiver. In oneembodiment, a mechanical leverage can be applied to the sides of thereceiver that are separated by slit 125 and which form front recess 122so as to pry them apart and allow the insertion of a barrel or barrelextension. When the prying force is removed, the sides can return andclamp the barrel or barrel extension into place.

As in the embodiments shown in FIGS. 1-5, there can be clamping holesformed in receiver 120, which are preferably perpendicular to thelongitudinal axis of front recess 122 along the length of front recess122. These clamping holes allow for the insertion of bolts, screws, orother appropriate fasteners through the front portion of receiver 120 toradially compress front recess 122 after a barrel or barrel extension istelescopically positioned within front recess 122. As noted above,although adequate compressive force against the barrel or barrelextension may be achieved by manufacturing a radially inward bias in thereceiver so that the at-rest position of front recess 122 is smallerthan the barrel or barrel extension radius, the use of appropriatefasteners as described above can aide in this compressive and clampingforce. Alternatively, the at-rest position of the receiver can besubstantially the same as the outer dimension of the barrel or barrelreceiver (as in the slip-fit arrangement described above), or greaterthan the barrel or barrel extension radius. In such cases, the fasteningmeans just described can be the sole source of compressive force. Ineither of the above three embodiments, however, adequate force isachieved through compression to hold the barrel in place. Because thecartridge to be fired is placed into the barrel or barrel extension, andit is the barrel or barrel extension which contains the explosivepressure of the ignited charge in the casing during firing, thereceiver's only job is to hold the barrel (and/or barrel extension) inplace with respect to the remaining parts of the rifle. The advantagesto this configuration will be discussed in more detail below.

Another advantage to the receiver configuration discussed above relatesto both ergonomic and safety advantages, particularly when the rifle isto be used for tactical purposes (although the advantages can be enjoyedfor both hunting and target shooting scenarios as well). This aspectconcerns the fact that the loading of a cartridge, as well as theunloading of a cartridge casing or an unfired cartridge, is preferablydone with minimal movement. The receiver configuration described aboveallows for minimal cartridge movement with minimal hand movement.Importantly, it allows for the ejection, by hand, of empty casings sothat, unlike the case with most prior art ejectors, the casing does notfly away from the weapon and operator, and risk sun glare reflection andthe position compromise associated therewith. Moreover, with the designnoted above, particularly in the embodiment with the slit and portdisposed at the bottom of the receiver, the operator can easily positionhis hand directly beneath the bottom opening to allow the cartridge orempty casing to drop directly into his hand or a positioned container asthe bolt is pulled rearward. Still another advantage is seen when anunfired cartridge is removed. Prior art rifles which forcibly eject liverounds risk unintended ignition of those live rounds when they strikethe ground. The present receiver configuration reduces such a riskconsiderably.

Still another advantage with the slit/open port configuration of thepresent invention relates to the manufacture and durability of therifle. The receiver of the present invention is not subject to forcesfrom the operating pressures of cartridge firing (except, of course, forrecoil related stresses). Because it is the barrel or barrel extensionwhich contains firing chamber pressures upon cartridge detonation, thereceiver component of the rifle according to the present inventionprovides a rigid housing from an alloy or polymer that is relativelyimmune to temperature, moisture, and stress failures, despite the lowoverall ultimate tensile strength of these materials compared totraditional steel. Due to the overall lower requirements for alloy orpolymer strength, there is no need to harden and temper the alloy orpolymer in order to increase its overall strength. In distinction, ofcourse, is the fact that hardening and tempering is a virtual necessityfor traditional steel receivers in order to increase the overallstrength of those receivers. Thus, the characteristics of appropriatealloys and polymers benefit overall weight, accuracy, reliability, wearreduction, and ease of manufacture. The light weight alloy or polymerused for the receiver of the present invention will allow for a receiversize which is dimensionally larger than the typical steel receivers andstock combinations but which will maintain a near equivalent weight.

As noted above, and as shown in FIG. 6, bolt 600 is shown removed frombolt clamping hole 610. Other compressive means could be used and canimagined by those skilled in the fastening art. A screw or bolt, withany head configuration, could be used. The number of fastening means andholes is also not critical, although the most preferred number is four.More than one hole is preferred so that should one fastener loosen, atleast one other will maintain the compression against the barrel orbarrel extension.

In addition to slit 125 allowing the necessary movement of front recess122 to allow insertion of the barrel or barrel extension, the fact thatslit 125 extends to load/eject recess 160 to form a single opening alongreceiver 120 is important to allow this movement. Because of theopenings in receiver 120 as discussed, much more “give” is provided foralong front recess 122 to allow the insertion of a barrel or barrelextension, as compared to the case where a slit would end at the back(or proximal) end of front recess 122. Moreover, the slit and load/ejectport combine to allow easier insertion of a barrel or barrel extensionby providing more flexibility within the frame of receiver 120 (ascompared to a slit alone).

Another benefit to the mechanical advantage gained by the slit/portcombination is seen with respect to the alignment of a barrel or barrelextension during insertion. It should be noted here that although theinvention concerns the insertion of a barrel or barrel extension,preferably a barrel extension will be what is inserted into receiver120. This is especially true in the case of larger caliber chamberings,such as the 0.50 BMG. In such cases, the barrel itself will be connectedto a thicker-walled barrel extension which houses the firing chamber.The thicker wall is necessary to withstand the pressures generatedduring firing of such chamberings. Thus, for purposes of thisdiscussion, the embodiment using a barrel extension (as is shown inFIG. 1) will be addressed. The invention is not necessarily limited,however, to situations where a barrel extension is inserted directlyinto the receiver of the present invention, but would include thosesituations where just a barrel is inserted, or where the barrel andbarrel extension may be integrally formed to form a single unitarybarrel with a flared end.

As shown in FIG. 7, barrel extension 700 is shown disposed opposite bolt710 which is the position of bolt 710 before bolt 710 is pushed forwardand rotated down into its battery position within barrel extension 700.The mating relationship between barrel extension 700 and bolt 710,particularly bolt head 720, is known to those skilled in the art. Inthis embodiment, barrel extension 700 is a metallic tube to which barrel730 is fixedly attached. Not shown in FIG. 7 is a cartridge which wouldbe inserted, as bolt 710 closes into battery, within barrel extension700 and perhaps part of barrel 730. Important in this embodiment isprotrusion 750 which is shown extending from the outer surface of barrelextension 700. In a preferred embodiment, protrusion 750 is a pin.

Protrusion 750 slides into and along slit 125 of front recess 122 ofreceiver 120 as barrel extension 700 is inserted into receiver 120during assembly/manufacture. This alignment is important because, asnoted above (and as shown in FIG. 7), bolt head 720 mates with barrelextension 700 during closing of the action as indicated by the arrow inFIG. 7. Because barrel 730 and barrel extension 700 are round, but thebolt head/barrel extension relationship is not, proper orientation ofthe barrel and barrel extension is necessary during assembly to achieveproper bolt/barrel extension alignment. This alignment is easilyrealized through the use of protrusion 750 and its relationship to slit125 during insertion of barrel extension 700 into receiver front recess122. Moreover, by providing protrusion 750 extending perpendicularlyfrom a tangent on barrel extension 700 (or directly from barrel 730 inan embodiment where no barrel extension is used), the barrel extensioncan be easily inserted into the receiver without the need for angularalignment gauges. The bolt head will always enter and exit the extensionopening without impacting the opening of the extension during use.Protrusion 750 is preferably a pin, as shown, but could take the form ofa rail or any other suitable guide.

Another aspect of the firearm assembly in accordance with the presentinvention relates further to the bolt itself and its relationship with ahammer. FIG. 8 shows a bolt in accordance with this aspect of theinvention. Specifically, FIG. 8 shows bolt 800 with bolt head 820disposed at its distal end. Also shown is handle 840. Within bolt 800 isa longitudinal channel disposed in the bolt to house a firing pin. Theproximal tip of the firing pin extends slightly proximal to the end ofthe firing pin channel and has a distal end at the bolt head and aproximate end extending out of the longitudinal channel to allowactivation of the firing pin by a hammer. In this embodiment, a recess850 is cut from a section of bolt 800 to allow access by a hammer (notshown) to the proximal end of the firing pin (not shown). In analternative embodiment, the proximal end of the firing pin could simplyextend out the back of bolt 800.

As can be seen in FIG. 8, safety bar 860 is disposed at the proximal endof the firing pin. When bolt 800 is in its open position, such as isshown in FIG. 8, safety bar 860 is rotated such that a hammer strike tothe bolt would impact a point indicated by reference numeral 870. Insuch a case, no movement of the firing pin would result because thehammer would not transfer a force to the proximal end of the firing pin.The hammer, in such case, would strike the bolt face at point 870 butnot the firing pin.

FIG. 9 shows the same bolt as that of FIG. 8, but which has been rotated90° into what would be a fully closed, or battery, position. As can beseen from FIG. 9, rotation of bolt 800 into a firing position rotatessafety bar 860 into an activation position whereby the firing pin can beactivated by a hammer striking and contacting safety bar 860 at point870. As noted above, bolt head 820 is also rotated into its batteryposition. Then, after firing, rotation of bolt 800 via handle 840 into anon-firing position rotates safety bar 860 out of the activationposition whereby a falling hammer cannot strike safety bar 860 and causeunintended firing.

The safety mechanism just described can be utilized in a firearm havingany degree of bolt rotation between a fully closed position (firingposition) and a fully open position. Typically this angle is between 60°and 100°. Preferably, the angle of rotation of the bolt between thefully closed position and fully open position, however, is between 85°and 95°, and most preferably it is 90°. Because of the safety mechanismjust described, however, the bolt does not have to rotate to its fullyopen position for the firearm to be in a non-firing condition.Preferably, the safety bar will move from its activation position (FIG.9) to a non-firing position by a bolt rotation of between only 20° and50°, preferably about 30°, from its fully closed position.

Although safety bar 860 is shown in the above embodiment as rectangular,a rounded edge embodiment, such as is shown in FIG. 10, could be used todecrease even further the chance of a hammer striking the firing pinuntil the bolt is completely (or nearly completely) closed. The use ofthis embodiment would mean that the safety bar will move from itsactivation position to a non-firing condition by only a small upwardbolt rotation, for example only 10°, from the bolt's fully closedposition.

Although the invention is illustrated and described herein withreference to specific embodiments, the invention is not intended to belimited to the details shown. Rather, various modifications may be madein the details within the scope and range of equivalents of the claimsand without departing from the invention.

1. A receiver for a firearm, said receiver comprising: a front, at leasttwo sides, and a bottom; a front recess to receive a barrel or barrelextension, said front recess defined by a channel in said receiver whichis open longitudinally along a longitudinal slit in said receiver; aload/eject recess open to said front recess and to at least one side orsaid bottom of said receiver, said load/eject recess sized to allow theinsertion and removal of a cartridge from said receiver; said slit andsaid load/eject recess together forming a single opening to saidreceiver whereby said receiver can expand to allow the insertion of abarrel or barrel extension into said front recess.
 2. The receiver ofclaim 1 wherein said slit and said load/eject recess are open to saidbottom of said receiver.
 3. The receiver of claim 1 further comprising aclamping hole in said receiver disposed through said longitudinal slit,said clamping hole sized to receive clamping means whereby said slit iscompressible by said clamping means to apply a compressive force on abarrel or barrel extension inserted into said front recess.
 4. Thereceiver of claim 2 wherein said clamping means is a bolt.
 5. Thereceiver of claim 1 wherein said front recess is sized to receive abarrel extension.
 6. The receiver of claim 2 wherein said receiver has aplurality of clamping holes.
 7. The receiver of claim 1 wherein saidreceiver is comprised of a material selected from the group consistingof aluminum, magnesium, or alloys comprised of aluminum or magnesium. 8.The receiver of claim 1 wherein said receiver is comprised of apolymeric material.
 9. A receiver for a firearm, said receivercomprising: a front and a bottom; a front recess to receive a barrelextension, said front recess defined by a channel open longitudinally atits bottom along a longitudinal slit; a load/eject recess open to saidfront recess and to said bottom of said receiver to allow the insertionand removal of a cartridge from said bottom of said receiver; and atleast one clamping hole in said receiver, said clamping hole disposedthrough said longitudinal slit, said clamping hole sized to receiveclamping means; said slit and said load/eject recess together forming asingle opening along said bottom of said receiver, and said front recessis expandable and contractible along said slit whereby said slit iscompressible by said clamping means to apply a compressive force on abarrel extension inserted into said front recess.
 10. The receiver ofclaim 9 further comprising clamping means.
 11. The receiver of claim 9wherein said receiver has a plurality of clamping holes.
 12. Thereceiver of claim 9 wherein said receiver is comprised of a materialselected from the group consisting of aluminum, magnesium, or alloyscomprised of aluminum or magnesium.
 13. The receiver of claim 9 whereinsaid receiver is comprised of a polymeric material.
 14. A barrelextension for a firearm barrel, said barrel extension comprising: ametallic tube having an outer surface; and a protrusion extendingradially outward from said outer surface of said metallic tube.
 15. Thebarrel extension of claim 14 wherein said protrusion is a pin.
 16. Asafety mechanism for a firearm to prevent unintentional firing of thefirearm, the safety mechanism comprising: a bolt having: a bolt headdisposed at a distal end, a proximal end, and a longitudinal channeldisposed in said bolt to house a firing pin; a firing pin disposed insaid longitudinal channel of said bolt, said firing pin having a distalend at said bolt head and a proximal end extending out of saidlongitudinal channel to allow activation of said firing pin by a hammer;a safety bar disposed at said proximal end of said firing pin whereinrotation of said bolt into a firing position rotates said safety barinto an activation position whereby said firing pin can be activated bya hammer striking said safety bar, and rotation of said bolt into anon-firing position rotates said safety bar out of said activationposition whereby a falling hammer cannot strike said safety bar orfiring pin.
 17. The safety mechanism of claim 16 wherein said safety baris rectangular.
 18. The safety mechanism of claim 16 wherein said safetybar has at least one curved edge.
 19. The safety mechanism of claim 16wherein the bolt rotation between said activation position and saidnon-firing position is an angle between 20° and 50° from the bolt'sfully closed position.
 20. The safety mechanism of claim 18 wherein thebolt rotation between said activation position and said non-firingposition is an angle between 10° and 20° from the bolt's fully closedposition.
 21. A firearm comprising: a barrel; a barrel extensionattached to said barrel, said barrel extension having a protrusionextending radially therefrom; and a receiver, said receiver comprising:a front, at least two sides, and a bottom; a front recess to receive abarrel or barrel extension, said front recess defined by a channel insaid receiver which is open longitudinally along a longitudinal slit insaid receiver; and a load/eject recess open to said front recess and toat least one side or said bottom of said receiver, said load/ejectrecess sized to allow the insertion and removal of a cartridge from saidreceiver; said slit and said load/eject recess together forming a singleopening to said receiver whereby said receiver can expand to allow theinsertion of a barrel or barrel extension into said front recess;whereby said slit accepts said protrusion to guide said barrel extensioninto said receiver.
 22. The firearm of claim 21 further comprising aclamping hole in said receiver disposed through said longitudinal slit,said clamping hole sized to receive clamping means whereby said slit iscompressible by said clamping means to apply a compressive force on saidbarrel extension.
 23. The firearm of claim 22 wherein said clampingmeans is a bolt.
 24. The firearm of claim 21 further comprising a safetymechanism, said safety mechanism comprising: a bolt having: a bolt headdisposed at a distal end, a proximal end, and a longitudinal channeldisposed in said bolt to house a firing pin; a firing pin disposed insaid longitudinal channel of said bolt, said firing pin having a distalend at said bolt head and a proximal end extending out of saidlongitudinal channel to allow activation of said firing pin by a hammer;and a safety bar disposed at said proximal end of said firing pinwherein rotation of said bolt into a firing position rotates said safetybar into an activation position whereby said firing pin can be activatedby a hammer striking said safety bar, and rotation of said bolt into anon-firing position rotates said safety bar out of said activationposition whereby a falling hammer cannot strike said safety bar orfiring pin.